Lengthy charging times have been a major obstacle to the adoption of electric vehicles. Now prestige car manufacturers are leading the way in fast-charge technology
How long does it take you to refuel your car? Admittedly, no one will get it down to the seconds expected by Formula One drivers, but most of us are also unwilling to sit and wait, perhaps at a public charging point halfway through our journey, while our electric car slowly recharges.
For years, charge times have been a key limiting factor for electric vehicles, particularly when compared with the familiar habit – and speed – of refilling a petrol tank. However, charging technology is evolving rapidly with researchers around the world racing to develop quicker systems, while also ensuring battery range is as high as possible.
“Charging technology is evolving rapidly with researchers around the world racing to develop quicker systems”
Several luxury cars are now able to achieve extremely rapid charges. Just over five minutes at a high-power charging station is all it takes for a Porsche Taycan to be recharged for a range of up to 100 kilometres. Aston Martin’s first all-electric vehicle, the Rapide E, has a high-voltage battery system that enables charging of 310 miles of range per hour using a 100kW delivery system. Meanwhile the limited-edition Lotus Evija all-electric hypercar requires just 12 minutes for an 80 per cent charge using 350kW charging technology, with a full charge taking around 18 minutes.
The science of power delivery
The time it takes to charge a car depends on several factors and engineers are attempting to refine each separate element. Charging with direct current (DC) is faster than with alternating current (AC). In addition, the higher the power (measured in kW) of a charging point, the quicker a car will be ready to drive again. The Lotus Evija, for example, also has the ability to accept an 800kW charge, which would replenish the battery in nine minutes.
“Charging with direct current (DC) is faster than with alternating current (AC)”
Researchers have therefore been working to develop charge points that are able to deliver DC at high power. Operating off the standard grid at home, an AC charger may be able to deliver around 7kW, which means it takes several hours to charge a car. However, high-voltage DC electric vehicle-charging stations can produce 50kW-350kW. The Ionity charging network, for example, a joint venture between Mercedes, BMW, Ford and Volkswagen that is being rolled out across Europe, can deliver charging power of up to 350kW.
Battery research is driven partly by the risk that regular high-speed charging will eventually damage the battery. Manufacturers often recommend not charging to 100 per cent every time but keeping the charge somewhere between 20 and 80 per cent of capacity for optimum performance.
However, research teams are also pushing these limits. Last year, a team at Pennsylvania State University announced a breakthrough in lithium-ion batteries after discovering that by heating up a battery while it is charging the process can be speeded up.
Traditionally, another limiting factor of battery design has been how long it takes to test new developments. Testing the lifespan of a newly designed battery to ensure it will satisfy consumers can take years. Earlier this year, however, a team from Stanford University announced it was using artificial intelligence (AI) to speed up battery testing.
“In battery testing, you have to try a massive number of things, because the performance you get will vary drastically,” says Stefano Ermon, a Stanford assistant professor of computer science. “With AI, we’re able to quickly identify the most promising approaches and cut out a lot of unnecessary experiments.”
“One day soon, you may find that your car has recharged before you even have time to grab a coffee at the service station”
The aim of all electric car manufacturers is to maximise convenience for consumers. By constantly finessing both batteries and charging systems, engineers are chipping away at the existing limitations. One day soon, you may find that your car has recharged before you even have time to grab a coffee at the service station.